Vista and XP don't waste as much ram as you think
A concept I've been preaching for years is that XP does not use more ram than Win 2000. Yes, if you view task manager you'll see that XP is using more ram than Win 2000, but that's because of pre-caching technologies. The truth is, if you take say a 128mb RAM computer and install 2000 and XP on it, XP will be faster. And if you tweak XP to disable services you don't need then it will be even faster. Honestly, after you tweak, XP will use less ram than 2000 if you take optionally cached ram out of the mix.
Well it's happening all over again in Vista but on a larger scale. I just read a good article that explains Vista's SuperFetch technology and if you're interested in understanding that Vista large ram footprint isn't bloat, it's system speed up.
http://www.tomshardware.com/2007/01/31/windows-vista-superfetch-and-readyboostanalyzed/
Near the end of the article they publish benchmarks, and show that apps that take 10secs to launch take only 2-3secs after SuperFetch learns how to pre-cache your apps. Saving 7 secs on app launch is a huge speedup in my book. Plus this article only continues to prove you want at least 1gb RAM for Vista, actually they recommend 2gb to get full speed benefits.